JP2690420B2 - Single crystal manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is mainly applied to GaAs and Ga.
P, GaSb. III- such as InAs, InP, InSb
Group V compound semiconductor single crystal, CdTe, Hg _1-x Cd _x T
e-, ZnSe and other II-VI group compound semiconductor single crystals using the vertical Bridgman method (VB method) or the vertical gradual cooling method (VGF).
Method).

[0002]

2. Description of the Related Art FIG. 7 is a sectional view of a conventional apparatus for the VGF method. A temperature gradient is formed in the protective cylinder 26 of the chamber 25 by the heaters 1 to 10 which are vertically divided into ten pieces.
A quartz tube 29 is placed at the center of this temperature gradient furnace, a solid high dissociation pressure element 20 is accommodated in a reservoir 19 connected therebelow, and a crucible 11 for accommodating a raw material melt in the quartz tube 29. The seed crystal 12 is placed at the lower end of the crucible 11.
Is placed, and the upper opening of the quartz tube 29 is sealed with a lid 30. After energizing the heaters 1 to 10 to completely melt the raw material, a predetermined temperature gradient is formed in the furnace, the crucible is rotated at the same height without being lowered, and the output of the heater is controlled to control the seed crystal side. Seed crystal 1 by gradually lowering the temperature from
From the upper end of 2, the raw material melt is cooled and solidified to grow the single crystal 21. During that time, the solid high dissociation pressure element 20 is vaporized in the quartz tube 29 to form a predetermined vapor pressure, so that it is possible to prevent the high dissociation pressure element from escaping from the raw material melt 28.

In contrast to the VGF method, the VB method is to obtain a single crystal by cooling and solidifying from the lower end of the crucible by gradually lowering the crucible while fixing the temperature gradient formed in the furnace. The VGF apparatus is different from the VGF apparatus in that crucible lowering means is provided, but the structure of the crucible, the container for enclosing the crucible, the heater and the like is almost the same.

[0004]

According to these crystal growth methods, a crystal with a low dislocation density can be grown by reducing the temperature gradient in the growth axis direction. Crystal defects such as twins and lineage are likely to occur. These defects can be suppressed from occurring by making the shape of the solid-liquid interface convex with respect to the melt, so that the shape control of the solid-liquid interface becomes very important. Therefore, insert a number of thermocouples directly above the solid-liquid interface of the raw material melt, measure the temperature distribution in the radial direction, and adjust the heater so that the shape of the solid-liquid interface becomes convex with respect to the melt. It has been previously proposed to adjust the power and to place a heater in the melt.

However, since the heater of the conventional temperature gradient furnace is divided and arranged in the growth axis direction, it is relatively easy to control the temperature gradient in the growth axis direction, but the temperature gradient in the radial direction is relatively easy. There is no suitable means to control
It was not possible to effectively prevent the occurrence of crystal defects such as twins and lineage. Therefore, the present invention uses the VB method or V
In the improvement of the apparatus for producing a single crystal by the GF method, the above-mentioned drawbacks are solved, the shape of the solid-liquid interface can be easily controlled, and the single crystal can be grown in a convex state with respect to the melt. It is intended to provide a manufacturing apparatus of

[0006]

SUMMARY OF THE INVENTION The present invention is an apparatus for producing a single crystal by having a vertical container for containing a raw material melt and a temperature gradient furnace, and cooling and solidifying the raw material melt from below. A stirring jig is arranged above the solid-liquid interface, one thermocouple is provided at the center of rotation of the stirring jig, and one or more thermocouples are arranged between the stirring jig and the inner wall of the crucible. It is an apparatus for producing a single crystal.

[0007]

FIG. 1 is a conceptual diagram of a single crystal production apparatus which is one embodiment of the present invention, and is an apparatus for carrying out the VGF method. The heaters 1 to 10 for forming a temperature gradient are arranged in the protective cylinder 26 of the chamber 25, while the solid high dissociation pressure element simple substance 20 is placed in the reservoir 19 at the bottom of the airtight container 13, and the crucible 11 is placed in the center. The seed crystal 12 is placed at the tip of the crucible 11, the raw material melt 28 is housed thereon, and the stirring jig 14 is placed in the raw material melt 28 to protect the stirring jig 14 at the center of the support shaft. A thermocouple 17 is arranged at the tip through the tube 15, and a protective tube 16 for the thermocouple 18 is provided near the wall of the crucible 11.
And the opening of the airtight container 13 is sealed with a lid 22. The lid 22 has a hole penetrating the support shaft of the stirring jig 14 and the protective tube 16 of the thermocouple 18, and a liquid reservoir for a liquid sealant is provided around the hole to seal the through hole. Also,
A liquid reservoir is also provided at the rear end of the support shaft of the stirring jig 14 to accommodate the liquid sealant and seal between the shaft and the protective tube 15. In this way, the thermocouples 17 and 18 can be moved up and down independently of the stirring jig, and the temperature distribution in the radial direction of the raw material melt at a desired height can be measured. Further, the airtight container 13 sealed as described above can control the output of the heater 1 to vaporize the solid high dissociation pressure element simple substance 20 in the reservoir 19 and secure the vapor pressure of the high dissociation pressure element. Dissociation of the raw material melt 28 is prevented.

FIG. 2 is a conceptual diagram of a single crystal manufacturing apparatus which is another specific example of the present invention, and is an apparatus for carrying out the VGF method. This apparatus is different from the apparatus of FIG. 1 in that the liquid sealant 24 is contained on the raw material melt 28 instead of omitting the airtight container to prevent the raw material melt 28 from dissociating. The configuration is the same as in FIG. Although the apparatus for the VB method is not shown in the drawing, the apparatus of FIG. 1 or 2 is provided with a crucible lifting mechanism, and other configurations are almost the same as the VGF apparatus.

FIG. 3 is a front view of the stirring jig, and FIG. 4 is a plan view of the stirring jig of FIG. This stirring jig has six propeller-shaped stirring blades at the lower end of the support shaft. FIG.
Is a front view of another stirring jig, and FIG. 6 is a plan view of the stirring jig of FIG. This stirring jig has a disc for stirring at the lower end of the support shaft.

The crucible of the present invention is made of PBN (Pyrolytic Boron Nitride), but quartz can also be used. Also, the airtight container is
It can be made of a member such as PBN, PG (pyrolytic graphite), vitrified carbon, PBN coated carbon, PG coated carbon, vitrified carbon coated carbon, stainless steel, molybdenum and the like. Further, the stirring jig can be made of quartz, PBN, PG, vitrified carbon, BN, SiC, Si ₃ N ₄ , AlN and those coated with carbon, or a metal such as stainless steel or molybdenum.

[0011]

【Example】

Example 1 A non-doped GaAs single crystal having a diameter of 3 inches was manufactured by the VGF method using the apparatus shown in FIG. The crucible is a PBN with an upper inner diameter of 85 mm and a lower inner diameter of 80 mm.
The bottom part was made into an inverted conical shape and a seed crystal was attached to the bottom end. Then, 7 kg of GaAs polycrystalline raw material was charged into the crucible. 50 g of solid arsenic was put into a reservoir of a carbon airtight container coated with PBN, and the crucible was set above it. Then, the propeller-shaped stirring jig made of PBN shown in FIGS. 3 and 4, the thermocouple provided at the axis of the jig and the thermocouple arranged near the inner wall of the crucible were inserted into the airtight container, and then the lid was closed. B ₂ O ₃ was stored in the liquid reservoir above the lid, and the chamber was sealed to complete the preparation.

In crystal growth, first, the inside of the chamber is evacuated to a vacuum, a heater around the lid of the airtight container is heated to soften and melt the liquid sealant B ₂ O ₃ contained in the liquid reservoir of the lid, and the airtight container Was completely sealed, the heater around the reservoir was heated to vaporize As, and the As partial pressure was adjusted to about 1 atm.
Then, the other heaters were also heated to melt the raw material in the crucible, and the chamber was filled with Ar gas to balance the pressure in the airtight container. After the raw material is melted, the stirring jig and the thermocouple are lowered to the growth interface, and the temperature is gradually lowered while maintaining the temperature gradient in the axial direction at the growth interface of 2 to 3 ° C./cm. Single crystals were grown. During the crystal growth, the position of the thermocouple was raised along with the movement of the growth interface so that the position was about 1 cm above the growth interface. Further, the rotation speed of the stirring jig was adjusted as shown in FIG. 8 so that the temperature of the thermocouple provided on the shaft of the stirring jig was about 0.5 ° C. lower than the temperature of the thermocouple provided around it. Specifically, after the crystal length has grown to 50 mm, the rotation of the stirring jig is started, the rotation speed is gradually increased, and when the crystal length reaches 250 mm, the rotation speed is 20 r.
By adjusting to pm, the temperature distribution of the growth interface could be adjusted as described above. By this adjustment, the shape of the growth interface could be controlled to have a gentle convex shape over the entire length of the crystal. As a result, a GaAs single crystal having a low dislocation density of 2 × 10 ³ cm ⁻² or less from the front to the back could be stably obtained. As a result of improving the controllability of the radial temperature distribution at the growth interface, defects such as twins and lineage were significantly reduced.

(Embodiment 2) A non-doped GaA having a diameter of 3 inches was measured by the VGF method using a liquid sealant in the apparatus shown in FIG.
s single crystal was produced. A crucible made of PBN having an upper inner diameter of 85 mm and a lower inner diameter of 80 mm was used, the lower portion had an inverted conical shape, and a seed crystal was attached to the lower end. Then, in the crucible, 7 kg of GaAs polycrystal raw material and liquid sealing agent B ₂ O ₃
300 g was added. Disk-shaped PBN shown in FIGS.
A stirring jig for production, a thermocouple provided on the axis of the jig, and a thermocouple arranged near the inner wall of the crucible were prepared above the crucible, and the chamber was sealed to complete the preparation.

In the crystal growth, first, the inside of the chamber was evacuated, Ar gas was introduced into the chamber, and the heater was heated to melt the raw material and the liquid sealant in the crucible. The Ar gas partial pressure in the chamber during crystal growth was adjusted to 5 atm. After melting the raw material, the stirring jig and the thermocouple are lowered to the growth interface, and the temperature is gradually lowered while maintaining the axial temperature gradient at the growth interface at 2 to 3 ° C./cm.
A GaAs single crystal having a length of about 250 mm was grown. During the crystal growth, the position of the thermocouple was raised along with the movement of the growth interface so that the position was about 1 cm above the growth interface. Also,
The rotation speed of the stirring jig was adjusted so that the temperature of the thermocouple provided on the shaft of the stirring jig was about 0.5 ° C. lower than the temperature of the thermocouple provided around it. By this adjustment, the shape of the growth interface could be controlled to have a gentle convex shape over the entire length of the crystal. As a result, the dislocation density from the front to the back is 2 ×
A GaAs single crystal with a low dislocation density of 10 ³ cm ⁻² or less could be stably obtained. As a result of improving the controllability of the radial temperature distribution at the growth interface, defects such as twins and lineage were significantly reduced.

[0015]

According to the present invention, by adopting the above-mentioned constitution, the number of revolutions of the stirring jig is adjusted so that the temperature of the thermocouple inserted on the growth interface of the raw material melt becomes the target temperature. As a result of easier control of liquid convection and more accurate control of temperature distribution at the growth interface, it is possible to maintain the shape of the growth interface gently downward and convex over the entire length of the crystal, and to prevent twinning. , It became possible to significantly suppress the occurrence of lineage. As a result, the productivity and the yield were remarkably improved, a crystal having a low dislocation density could be stably obtained over the entire crystal, and there was a remarkable effect in improving the quality.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a single crystal manufacturing apparatus that is an embodiment of the present invention.

FIG. 2 is a conceptual diagram of a single crystal manufacturing apparatus that is another embodiment of the present invention.

FIG. 3 is a front sectional view of a stirring jig used in the apparatus of the present invention.

FIG. 4 is a plan view of FIG. 3;

FIG. 5 is a front sectional view of another stirring jig used in the apparatus of the present invention.

FIG. 6 is a plan view of FIG. 5;

FIG. 7 is a conceptual diagram of a conventional single crystal manufacturing apparatus.

FIG. 8 is a graph showing an example of controlling the rotation speed of a stirring jig.

Claims (2)

(57) [Claims] 1. An apparatus for producing a single crystal by cooling and solidifying a raw material melt from below in a vertical container for containing the raw material melt and a temperature gradient furnace, wherein a stirring jig is provided above a solid-liquid interface. Is provided, and one thermocouple is provided at the center of rotation of the stirring jig,
An apparatus for producing a single crystal, wherein one or more thermocouples are arranged between the stirring jig and the inner wall of the crucible. 2. The vertical container is contained in an airtight container, a high dissociation pressure component element simple substance is arranged at the bottom of the airtight container, a liquid reservoir is provided on the lid of the airtight container, and a drive shaft for the stirring jig and 2. A thermocouple protection tube is provided with a liquid reservoir around a hole penetrating the lid of the airtight container, and airtightness is maintained by a liquid sealant contained in the liquid reservoir. Single crystal manufacturing equipment.